A) Field of the Invention
The present invention relates to a ball-transfer mechanism having a brake mechanism and a vehicle employing the ball-transfer mechanism.
B) Description of the Related Art
A ball-transfer mechanism is a roller device which allows a vehicle to move in any direction relative to a generally level surface. Such a ball-transfer mechanism has a structure, for example, as shown in FIG. 9. The ball-transfer mechanism shown in FIG. 9, is designated by the reference numeral 91 and is used, for example, as one of several wheels on an industrial flat car which is movable in any direction on a generally level surface 99. A large ball 95 which contacts the level surface 99 is configured to roll in any direction while supported by a main body 92. The ball-transfer mechanism 91 includes the main body 92 and a supporting member 94 disposed within the main body 92. A space 92a is defined between the supporting member 94 and an inner portion of the main body 92. An upper portion of the space 92a has a generally spherical shape, with lower portions of the space 92a having an annular shape open to the portion of the main body 92 where the large ball 95 is located.
A plurality of small balls 96 are retained within the space 92a and in the space between the supporting member 94 and the large ball 95. The small balls 96 may roll around edges of the supporting member 94 such that the small balls 96 are freely disposed between the supporting member 94 and the large ball 95.
The small balls 96 follow rolling movement of the large ball 95 and must withstand forces associated with the loads acting on the large ball 95. In other words, the small balls 96 provide support for the ball-transfer mechanism 91, allowing the large ball 95 to rotate in various directions within the main body 92.
When a small ball 96 enters the space 92a, the small ball 96 no longer receives the loads or forces from the large ball 95. Within the space 92a, the primary force acting on the small balls 96 is gravity. Therefore, within the space 92a, the small balls 96 naturally tend to move downward (relative to FIG. 9) and further tend to move toward areas where the least number of other small balls 96 are located. For example, the small balls 96 can easily move to an opposite side of a center axis 91a, resulting in allowing the large ball 95 to roll inside of the main body 92.
When a ball-transfer mechanism, such as that described above, is used on a flat car or other such rolling device, a brake device needs to be added to the flat car because such ball-transfer mechanisms do not have a brake function.
Although a ball-transfer mechanism provides many benefits such as being able to move in any direction, one disadvantage is that there is no direction stably during movement and not braking function.
Another means of allowing a flat car or vehicle to roll is employment of a caster installed on, for instance, a wheel chair such as that shown in FIGS. 16 and 17. FIGS. 16 and 17 shown a schematic drawing of a conventional electromotive wheelchair. As shown in FIGS. 16 and 17, a pair of casters 191 are mounted on the underside of a wheelchair 190. One caster 191 is disposed on a left front side thereof and one caster 191 is disposed on a right front side thereof. As a result, the wheelchair 190 can go straight or back and circle by controlling only two motors 193, each motor 193 connected to corresponding rear wheels 192. The caster 191 can rotate freely about an axis 191a. Rotation about the axis 191a is indicated generally in FIG. 17 by the arrows in FIG. 17.
The wheelchair 190 described above can keep going straight on a paved flat road without any problems.
However, when it goes across an inclined road or goes on a rough road, the wheelchair 190 might not go straight because the caster 191 rotates about the axis 191a. When the caster 191 roles on an inclined surface or rough road, the caster 191 often has difficulty with continued stable rolling.